Chaperone proteins aid in the trafficking, post-processing, disentanglement and folding of biomolecules such as proteins and possibly nucleic acids in vivo. This function can be viewed as the last step in signal transduction, as an expressed but improperly folded biomolecule is of no function to the cell. Therefore, detailed understanding of the influences of chaperone proteins on the in-vivo folding process is of importance to the understanding of complicated cellular regulation and growth cycles. We propose to focus on the interaction of Hsp70-heatshock- chaperone proteins with peptides and other proteins in detail using a small 14 kDa Hsp70 construct. This size reduction was conceived on the basis of the structural studies of larger domains in the previous period. We aim to understand the interaction between this Hsp70 domain and a substrate protein in a complex of manageable size. This will reveal how chaperone proteins help disentangle misfolded proteins and what defines folding-prone structures. A newly discovered heatshock protein, Hsp15, which is likely part of the developing ribosome, displays RNA-specific binding and moderate RNA-chaperoning activity. We propose to obtain a detailed description of the interaction between this protein and RNA in terms of structure, dynamics and energetics. This will help better understand the underlying principles of RNA-protein interactions in general. By comparing results on the Hsp15 and Hsp70 proteins, which share the property of being heatshock proteins with chaperone activity, but differ by their target substrates, we aim to learn what the points of similarity and difference are. This knowledge will help understand biomolecular interactions in general.